Nickolas's blog

April Fools Day Contest 2019
By Nickolas, 6 years ago, translation, In English

The contest is over; I hope at least some of you enjoyed it :-) The editorial is published here.

The 7th April Fools Day Contest will take place on Monday April 1st. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.

In this round you'll be given several weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces. To get an idea of what the contest will look like, you can check out the contests of the past years: 2012, 2013, 2014, 2016, 2017, 2018.

As usual, to enjoy competing in this round you'll need a sense of humor compatible with mine. Good luck, and have fun!

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Comments Comments (140)
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6 years ago, # |
  Vote: I like it +1 Vote: I do not like it

surprisingly tough ....XD

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6 years ago, # |
  Vote: I like it +45 Vote: I do not like it

It's humor and Accepted that create fun.

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6 years ago, # |
  Vote: I like it +17 Vote: I do not like it

The best contest of the year :D (not that I perform well in it)

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    6 years ago, # ^ |
      Vote: I like it +113 Vote: I do not like it

    I take back my comment.

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      6 years ago, # ^ |
        Vote: I like it +11 Vote: I do not like it

      before contest: so excited !!! after contest: whatever :)))))

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        6 years ago, # ^ |
          Vote: I like it +65 Vote: I do not like it

        Trying to solve those yes/no problems gets boring quickly when every hypothesis you make turns out to be wrong.

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6 years ago, # |
  Vote: I like it +20 Vote: I do not like it

ravioli ravioli, what is in my 1st april contestoly?

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6 years ago, # |
  Vote: I like it +3 Vote: I do not like it

I have been waiting for this contest

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Will this year have April Fool's contests on other platforms? Last year there were other 2 big ones at least, but I couldn't find any this time.

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6 years ago, # |
  Vote: I like it -7 Vote: I do not like it

Is it rated?

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6 years ago, # |
← Rev. 2   Vote: I like it -8 Vote: I do not like it

.

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6 years ago, # |
  Vote: I like it +48 Vote: I do not like it

Unrated:Let's solve the problems just for fun!I hope everybody have fun.XD

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6 years ago, # |
  Vote: I like it +61 Vote: I do not like it

No problem statements plz

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    6 years ago, # ^ |
      Vote: I like it +52 Vote: I do not like it

    I am tempted to follow this request, since for one of the problems writing the statement (in two languages) took strictly longer than writing all other pieces of the problem, and it certainly will be the case for another problem... But alas, I aim for variety of jokes above all, so some of the problems have to have a statement :-)

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6 years ago, # |
  Vote: I like it +42 Vote: I do not like it

"When the contest begins" Surprise! There is no contest :)

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    6 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    "There is contest after 30 minutes, let's open cf" Boom!

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6 years ago, # |
  Vote: I like it -68 Vote: I do not like it

Nobody:

Me:

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6 years ago, # |
  Vote: I like it +15 Vote: I do not like it

A classified source just confirmed that this round will be rated :P :P :P

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6 years ago, # |
  Vote: I like it +22 Vote: I do not like it

It's April Fools, so during the contest suddenly it will become rated =)

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6 years ago, # |
  Vote: I like it -8 Vote: I do not like it

Why unrated? :(

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6 years ago, # |
  Vote: I like it +2 Vote: I do not like it

It's April 1st, the contest may suddenly starts 2 hour earlier XD

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6 years ago, # |
  Vote: I like it +7 Vote: I do not like it

2012,2013,2014-2016,2017,2018 Mathematically, u shouldnt be doing an april-fools contest this year o.O

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6 years ago, # |
← Rev. 2   Vote: I like it +36 Vote: I do not like it

I hope, in this year, this will not happen with me ...

Capture
image uploading site

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    6 years ago, # ^ |
    ← Rev. 2   Vote: I like it +8 Vote: I do not like it

    It was normal that you got wrong answer. You had to make a program that makes 2 good bets in roulette. The results were made randomly (like in normal roulette). The best strategy was to bet on red or black (even or odd), because you have 48.6% that your bet will be good. That means 23.6% chance to pass main tests (only 2 test cases). While the results were random, the Answer section were made by the code of author that got accepted, so that can't be always good. In your case the result was 10 (black), so you got WA.

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    so, can I ask what is the contest id of the problem?

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6 years ago, # |
← Rev. 2   Vote: I like it +57 Vote: I do not like it

To all the other teams which are attending ICPC WF, let's join this contest together!

Spoiler
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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Exciting！

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6 years ago, # |
← Rev. 2   Vote: I like it -8 Vote: I do not like it

This is my first April Fool's Day contest. exciting!!!

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6 years ago, # |
← Rev. 4   Vote: I like it 0 Vote: I do not like it

Fools Day happy~~ : )

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6 years ago, # |
  Vote: I like it +11 Vote: I do not like it

This contest won't get rated afterwards, right?

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    6 years ago, # ^ |
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    No one knows. It is April's fools contest, anything can happen :D

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6 years ago, # |
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I hope I won't become a fool after this contest :3

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6 years ago, # |
← Rev. 2   Vote: I like it +75 Vote: I do not like it

The 7th April Fools Day Contest will take place on Monday April 1st.

Nickolas It's 32nd march, fix it.

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6 years ago, # |
  Vote: I like it -14 Vote: I do not like it

Is it rated??

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6 years ago, # |
  Vote: I like it -12 Vote: I do not like it

real fun

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6 years ago, # |
← Rev. 2   Vote: I like it -18 Vote: I do not like it

chutiyaap

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6 years ago, # |
← Rev. 5   Vote: I like it 0 Vote: I do not like it

(https://drive.google.com/open?id=1BEDXr5N2ZR5Hf5Q4jHsbAxPjX69aO-Pu)

Spoiler
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6 years ago, # |
  Vote: I like it +97 Vote: I do not like it

Goodluck and have fun everybody!

2xh1p7

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

It is should be April fools night contest for me :3

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6 years ago, # |
  Vote: I like it +11 Vote: I do not like it

The image in the Russian version of 1145C - Mystery Circuit is broken for some reason, here is what it should be:

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    6 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    Should've supported Q# submission, missed opportunity. Tssk tssk.

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6 years ago, # |
  Vote: I like it +1 Vote: I do not like it

It's the first time I get rank1.

I'm so happy.

XD

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Wonder how the editorial will look like...

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6 years ago, # |
  Vote: I like it +1 Vote: I do not like it

D has great speiling

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6 years ago, # |
  Vote: I like it +137 Vote: I do not like it

Due to the unethical and ugly behavior of some members of the community, this round will be rated. Let's solve problems just for fun!

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6 years ago, # |
← Rev. 2   Vote: I like it +9 Vote: I do not like it

Please post the editorial as soon as possible. Eagerly waiting (to submit :P).

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6 years ago, # |
  Vote: I like it +4 Vote: I do not like it

How are so many people solving D can anyone post the answer :D :P

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6 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Toughest Constest ever
Can't even go through the problem statements.

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6 years ago, # |
  Vote: I like it +40 Vote: I do not like it

I have seen some previous years April Fools Contest problems but this is the lamest April Fools Contest of all time. No offence

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6 years ago, # |
  Vote: I like it +22 Vote: I do not like it

Tutorial for problem B please :)

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6 years ago, # |
← Rev. 2   Vote: I like it +11 Vote: I do not like it

I made a bet with my senior ray-asuka that if I could not become a candidate master before my birthday（4.2）, I would invite him and my teammates to dinner. This round was my last chance, and he got his wish.

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Paper

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6 years ago, # |
  Vote: I like it +8 Vote: I do not like it

Felling like a real fool :(

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6 years ago, # |
  Vote: I like it +24 Vote: I do not like it

two plus xor of third and min element?

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    YES!

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    6 years ago, # ^ |
      Vote: I like it +28 Vote: I do not like it

    how did you even come up with that solution?

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    6 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    How did people guess this on the first attempt, with only one sample case?

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      6 years ago, # ^ |
      ← Rev. 2   Vote: I like it +3 Vote: I do not like it

      It's the wrong letters, they make up sentence.

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      6 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      exactly !! how ??
      Xor seems intuitive... but what about min^3rd + 2 ...
      Its impossible without extra hints

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      6 years ago, # ^ |
        Vote: I like it +2 Vote: I do not like it

      Note that there are typos in the statement. Write down all the letters that should be replaced by some other letter for the correct spelling. This is the message you get.

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6 years ago, # |
  Vote: I like it +40 Vote: I do not like it

My solution for E: if $$$i$$$ gives remainder 1, 4 or 5 mod 6, then yes. Sadly, it's a wrong solution, but it perfectly fits.

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6 years ago, # |
← Rev. 3   Vote: I like it +35 Vote: I do not like it

((min(id,25)+id)%(2+id%3))>0

I found it after 1min of the contest...

THAT'S AWESOME!

UPD: Problem E

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    6 years ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    And where did this magical condition come from?

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      6 years ago, # ^ |
      ← Rev. 2   Vote: I like it +26 Vote: I do not like it

      It comes from the Fourier transformation of the image 1 to 20. (my poor English :D

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    6 years ago, # ^ |
      Vote: I like it +29 Vote: I do not like it
    $$$\{[\min(\mathrm{id},25)+\mathrm{id}]\bmod(2+\mathrm{id}\bmod3)\}>0$$$

    That's neat!

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6 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Well, I managed to brute force B after 50 attempts...

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    6 years ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    i do the same for problem C :)

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      6 years ago, # ^ |
        Vote: I like it +15 Vote: I do not like it

      I made the same for both :P

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      6 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      How do you bruteforce C when you need to guess a number? Seems like it would take a lot more attempts :o

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        6 years ago, # ^ |
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        Tests turned out to be ordered by numbers in their input)

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        6 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        I made it with supposing that the answer is also between 0 and 15. I wasn't sure on it, but I tried it. Later I noticed that each number has different answer.

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        6 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        Input has 4 bit. Circuit looks like some kind of bit shuffling / adding. So we can guess that output is in range [0, 15] and has some kind of pattern.

        --> basically just submit some educated guess. You can look at my submissions to see how I guessed it.

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    curious about how to brute force on YES/NO problems

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      6 years ago, # ^ |
      ← Rev. 2   Vote: I like it +5 Vote: I do not like it

      Make sure it answers correctly for first 4 tests. Then try to get 5th test with binary search — answer no to everything (else), then yes to 50..99, etc. Eventually I realized the test cases are in increasing order which made things a lot easier — just need to find the next value to "flip" the answer on.

      That's pointless on any serious contest because the number of attempts it takes will give you around 0 points.

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6 years ago, # |
  Vote: I like it +110 Vote: I do not like it

You: TWOPLUSXOROFTHIRDANDMINELEMENT

Me, an intellectual: LTABRACCANEPGZEFBOHPNOSIFASOMC

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    6 years ago, # ^ |
      Vote: I like it +37 Vote: I do not like it

    An intelleqtual

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    6 years ago, # ^ |
      Vote: I like it +14 Vote: I do not like it

    I knew this fact quickly because i use google translator... kk

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    And wtf is that "mine element" :|? Got this message pretty quickly but had no idea what to do with it.

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      6 years ago, # ^ |
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      Notice how there is only 1 e, not 2 e(minelement isn't mineelement).

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      6 years ago, # ^ |
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      I guess it is "min" element. btw which message are you talking about?

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        6 years ago, # ^ |
          Vote: I like it +1 Vote: I do not like it

        By message I meant hidden statement "two plus (...)"

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      6 years ago, # ^ |
        Vote: I like it +10 Vote: I do not like it

      fece is a correct word, so MIN element ...

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        6 years ago, # ^ |
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        ... but it took me half an hour to figure it out :D Also had MINE there at first ...

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    6 years ago, # ^ |
      Vote: I like it +18 Vote: I do not like it

    SBEVE

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6 years ago, # |
← Rev. 3   Vote: I like it -8 Vote: I do not like it

1% of time to read statements, 99% of time to guess and attempt, lol

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    6 years ago, # ^ |
    ← Rev. 2   Vote: I like it +8 Vote: I do not like it

    You missed 1% (I wrote it before he edited his comment).

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Why can't I view others' solutions? System Checks?

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Only one task... Ahahahah, the best contest)) I want more!

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

my wrong solution for C: A circle with cross indicates 4(because of cross); A dot indicates 1(because it's a dot); Note that the input number is between 0 and 15, so make it become binaries. for the example: 3->0011->the last line(4+1+1+1) + the third line(4+1+1) =13;

I think this is reasonable but got WA , sad...

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6 years ago, # |
  Vote: I like it +30 Vote: I do not like it

Use the most foolish way to spend April Fools' Day lol！！！

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6 years ago, # |
← Rev. 2   Vote: I like it +35 Vote: I do not like it

I am so happy to be the second person to solve problem C!!

All because I listened carefully in the [Quantum Computing] class when COIWC2019(Chinese Olympiad in Informatics — Winter Camp)!!

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6 years ago, # |
  Vote: I like it +73 Vote: I do not like it

Why the problem B wants to ban KAN? Just a joke

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

in D i used grammarly to get the grammatically correct sentence to make it readable. rip

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6 years ago, # |
  Vote: I like it -26 Vote: I do not like it

Solution of A:N/4

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    really? i brute forced the whole solution :P

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    In the first test case n was 4 but the answer was 4 not 1

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Now I regret because I voted that I love this contest before it starts..

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Please help in problem A.

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    In each step, delete either the right half of the matrix or the left In order to get a part of the numbers ascending sorted Print the longest length of a sorted array you can obtain

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6 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Problem A is straightforward — no sense of humor required to solve it.

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Will the links to contestant solutions be available?

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    6 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    You should be able to see the solutions now.

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

congrats to applese for winning the 2019 fools contest!

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6 years ago, # |
  Vote: I like it 0 Vote: I do not like it

We are used to look for the editorial in the end of the post, not in the beginning.

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